Sprocket fastening means



May 12, 1953 H. F. HEIDEGGER SPROCKET FASTENING MEANS Filed Feb.-25, 1949 ENTOR l N V HENKYF/ /EIDEGGEIQ ATTORN Y Patented May 12, ,1953

. sritooka'ri sifigi M S} v I to International Projector Corporation, Bloomfield, N. J., a corporation of Delaware Application February 25, 1949, Serial No. 78,277

'3 Claims. (01. {zen-$ This invention relatesto improvements in sprocket fastening means, and is especiallydiliectedto a novel means for removably attaching arotatable driving element, such as a film-feeding sprocket, or the like,' to its shaft.

, Although the invention is susceptible of use .in mounting a great variety of sprockets, pulleys, or hubbed. gears on their shafts, it is particularly suited foruse in mounting film-feeding sprockets 'on' their shafts,. as indicatedin U. S. Patent No. 2,312,760! issued to me on MarchiZ, 1943 and upon which the present invention is an improvement. In motion picture projecting machines'the film passes over and under successive, continuously running and intermittently. rotating toothed sprockets, the teeth of which enter sprocket holes formed in one 01 both margins ofthe film. The film is held engaged with the teeth by suitably supported; grooved guide or pad rollersembracing the circular series of teeth onthe rims of thespr'ockets, there being aslight clearance; between the pad rollers and toothed end flanges of the sprockets to avoid pinching the film; 3

To speedup the manufacture of sprockets for use in "motion picture projectingmachines, resort has been made to breaching and reaming the axially extending bores. Any bore thatis broached is slightly barrel-shaped because such operationpushes the metal aside or-compacts the metal; instead of cleanly'removing it as would be the case if the bores were drilled, and' as the bro aching pressure is removed when the operation has been completed, themetal tends slight 1y to return to'its former position- Barrel-shaped bores are not readily detected by the usual gauges 'because the oppositeopen ends of the bores are generally ofzthe correct diameter after reaming. When a sprocket having a slightly barrelshapedbearing is'mounted on a-rotatable shaft ittends to run out -or have an ellipticalorbit or wobble when firmly, secured to its shaft. The use of such a sprocket in connection with the usual guide and-film-retaining rollers is likely to patched portions of the film-are liable to catch on the pad rollers and betorn. Otherobjectionsreside in the usual"methods heretofore lli d 1 0' -.-ri gidl y 'securey.1-,h ;=tmm

result inpinching the film between the pa'dfor sprockets to their shafts. .For example, it has been customary to attach the sprocket wheels to their shafts 'by ordinary set screws threaded into radial holes drilled into the longitudinal boresof the sprockets at points between the ends of the sprockets, the inner ends of the set screws bearing firmly against'the peripheries ortheir shafts. .This simple methodof fastening the sproi'a kets to their shafts was intended tdenable the sprockets to be readily removed and replaced for repairs or to obtainaccess to other mechanism behind the sprockets. One objection'tothis method is that when'the retaining set screw is turned down tightly on the periphery of the "shaft it tends to bend the shaft. Since the bores of. the sprockets are formedflslightly larger in diameter thanthe diameter of the shaft so as to readily slip'onto their shafts this method of fastening takes up 'thefclearance along one side of the sprocket and increases the clearance on the diametrically opposite side, resulting in'eccen} trically positioning the sprocket on theshaft. ;Asiinilar result occurs if areverse arrangementbe resorted to wherein the radial holein the sprocket is'unthreaded, but is shouldered or counter-bored and a threaded hole formed radial- 1y of the shaft. The'radial holes in the sprocket and haft are aligned and a headed'set tered" in the unthreaded counter-bored sprocket hole and screwed intothe threaded hole in'the shaft. When the screw is tightened with its head'a'gainst the shoulder in the counterboredsprockethole theshaft is drawn towards thescrevv instead of being forced away, butthe same eccentric positioning of "the sprocket on the clearance provided shaft occurs because of the as above explained.

Another objection presenti'n the stfscrw method of securing pulleys, Sprockets and "the like "directly "onto shafts 7 is that whensettin'g the screw fast on the shaft, the rorcerequired to firmly engage the screw with the shaft not on1y cause's the end of the screw to indent the shaft but as-thescrew is given the last turn ortur'ns, the end of the screw raisesa bur 'on'the shaft which for'ms an obstruction preventing the "attached'sprocket or the like from being-readily slid off the shaft, and, of course, opposes the placing of a sprocket on theshaft; One principalobject of the present invention is to provide means to attach a sprocketor gear proper position on a shaft by'novel'm'eans which avoids the foregoing disadv'antagesand retains the advantageof ease of applying and removing; .I. i' Thus, theimprovement constituting the pres ent invention provides novel means for retaining the sprocket or analogous part on a shaft against relative rotation, in such a manner as to avoid not only an eccentric mounting of the sprocket, but also the danger of bending the shaft heretofore incident to the former methods of securing the part to the shaft. This'improvement is attained by mounting the sprocket loosely on its shaft while providing for the resilient and adjustable centering of the part on the shaft, instead of fastening the part tightly on the shaft as practical heretofore. By thus mounting the sprocket on its shaft, the sprocket can automatically center itself or maintain concentricity with the shaft, which affords the sprocket a radial self-adjustment relatively to the shaft.

Other objects and advantages will be more fully set forth hereinafter and-particularly pointed out in the claims.

In the accompanying drawings,

Fig. 1 is a longitudinal view, partly in section, showing one form of the invention;

Fig. 2 is a cross-sectional view on line 2-2 of Fig. 1.

The present invention is designed as an improvement over prior inventions of similar nature by avoidingthe necessity for firmly clamping the sprocket frictionally or otherwise to the shaft to secure the sprocket and shaft fixedly together as a substantially integral unit.

Instead, according to this invention, the shaft is entirely relieved of any radial pressure or stress in its relation with the sprocket, thecon nection of the sprocket with the. shaft being effected by utilizin a wholly different principle, which not only avoids any damage to the shaft, but also requires little if any change in the sprocket, and enables the sprocket, in operation, to. automatically maintain its concentricity with the shaft.

To. these and other ends, in the form of the invention shown in Figs. 1 and 2, the shaft I I, driven from any suitable source of power, not shown, is revolubly mounted in a bearing or bushing 3d supported in hollow bosses 3-I, (II projecting from opposite faces of the sub-frame I4 of..amotion picture projecting machine.

Oneend of the shaft II projects beyond the boss 3!, and is annularly grooved, asat 20, at a point near the outer end of the boss 3|. That portion of the projecting end of the shaft extending beyond the annular groove constitutes the support for the sprocket I3, and-is provided with a longitudinally extending key way I5. embraced by the bore I2 of the sprocket. The key way extends to the free end of the shaft II to provide an open end to slidingly accommodate the inner end of a pre-set key I 5 mounted in the bore of the sprocket.

While it might be possible to utilizea sprocket I3 provided with a radial, threaded hole extending from the periphery of the sprocket into the bore of the sprocket to accommodate a threaded screw It which might be turned down until its inner end enters the key way I5, but not far enough to apply pressure to, or prevent radial movement of the sprocket on the shaft, there remains the possibility that the screw might accidentally work loose and damage the film, as well asreleasing the sprocket from its shaft, by its withdrawal from the key way I5. To avoid this possible failure, the sprocket I13, shown in Fig; 1, is provided with a drilled hole or passage23 extending radially of the sprocket and located about midway of the ends thereof, the inner end of the passage 23 opening into the bore I2 of the sprocket. Into this passage is driven a cylindrical key-pin I8 of a slightly greater crosssectional area than the cross-sectional area of the passage, to maintain a driving fit.

The inner end of the key-pin is turned down or reducedin size, as at I1, to a diameter very slightly less than the width of the key way I5, so as to slidingly fit in the key way with as little clearance as possible, to prevent relative rotary movement between the shaft and sprocket, and yet permit the sprocket to slide longitudinally of the shaft in assembling and disassembling the parts and for relatively centering the sprocket and film.

The key-pin IBprojects into the bore I2 of the sprocket sufficiently to maintain its engagement with the key way I5 and leave a slight clearance between the. extreme end .of the key-pin and the bottom of the key-way, to permit the sprocket or other rotated elementlto have a slight play of a thousandth of an inch or two, relatively to the shaft I If in. a radial direction, enabling the sprocket to automaticallycenter itself relatively to the shaft, without disconnecting the key from its key way. Thus, full engagement of the. sprocket and film is maintained at all times, even with sprockets having. barrel-shaped bores.

The reduced end of the key-pin I6 has a further function. In driving the key-pin I6 into place, it forces aheadof it, a slight bur of metal scraped from the wall of the passage 23. If the entire key-pin were uniformly cylindrical, this bur'would be forced into the bore I? of the shaft where it wouldfinterfere with the bearing of' the sprocket on the shaft, and with sliding the sprocketon and off the shaft. By reducing the inner end of the keypin, as at 11., the scraping action is now performed by the shoulder at the juncture ofthe reduced'end II'with the body I6 of the key-pin, apart. fromthe extreme inner end, instead of by the inner end, and the reduced inner end of the key-pin provides an annular space ahead of-the shoulder to accommodate the bur of metal scraped from the wall of the passage 23,*so that it does not enter the. bore of the sprocket.

The extremefree end of the shaft, is provided with a threaded hole 22 extendinglongitudinally into the shaft to accommodate the threaded stem of a cap screw I8, the cap or head 24 of which is substantially greater in diameter than the diameter of the-shaft. The threaded screw hole 22 is deeper than the-length of the stem of the cap screw it sothat when thezcap screw is applied,.the inner'face of the head 24 will contact the free end of the shaft.

In assembling the sprocket on the shaft, a hardenedweamr'esistant washer 33, having a hole slightly larger in diameter t-hanthediam'eter of the shaft, is first slid onto the shaft II to a position'between the-annular-groove 20 and the exposed end'of'the'bearingv sleeve 30. Next,asnap ring or split ring washer'34 of larger over-all diameter than the shaft, and having its central opening of a diameter slightly less than the diameter of the shaft, the ring or Washer being of a width substantially corresponding with the width of the groove 20, is sprung or fitted into the groove to over-lap and hold the wear resistant washer 33 in place.

Thereafter, a cupped spring washer I9 is slipped over the outer'end of the; shaft and slid along the shaft until it contacts the outer face of the split ring 34.

The sprocket I3, with its press-fitted key-pin I6 pre-set to gauge, the inner end of which pin projects into the bore I2 of the sprocket, is positioned with its bore I2 in line with the shaft and with the round, inner reduced end of the key-pin I6 in line with the open end of the key way I5, and then slid onto the shaft until the inner flange or end of the sprocket contacts the cupped spring washer l9.

Thereafter, the headed cap screw I3 is screwed in place in the threaded hole 22. As the cap screw is turned down, its broad head 24 presses against the outer flanged end of the sprocket to 'maintain the inner end of the sprocket in contact with the cupped spring washer I9 which latter is backed against the snap ring 34.

The wear-resistant washer 33 protects the protruding end of the shaft bushing 30 from being scratched or mutilated by the sharp edges of the snap ring 34.

The headed cap. screw I8, 24 retains the sprocket against sliding off the free end of the shaft, and the cupped spring Washer 19 tensioned by the pressure of the cap screw head against the sprocket, maintains the sprocket against the inner face of the cap screw head 24 to oppose the longitudinal movement of the sprocket inwardly along the shaft.

It will be clear from th foregoing that this invention permits the sprocket to center itself relatively to the shaft, to maintain concentricity therewith, and also avoids bending, or the imposition of any other strain transversely of the shaft.

It is also seen that the pre-positioned or preset key-pin I6, I! slides freely along the openended key-way I in the shaft, and that this key-pin connection transmits rotary movement from the shaft to the sprocket, avoiding the setscrew connection heretofore used.

Furthermore, the head of the cap screw in conjunction with the cupped spring I9 tensioned by the same cap screw, holds the outer end of the sprocket even with the free end of the shaft, where it is in proper position relatively to the film path, so that a proper alignment of the film will be maintained as it is fed from one sprocket to another and to the take-up magazine.

' Heretofore, considerable time and labor has been expended in the production of accurate sprockets and sprocket shafts in the motion picture industry to provide precisely designed parts, which, when assembled according to former methods, run out of true despite the care used, because of the fastening means employed to secure the parts fixedly together against relative movement. A tolerance of one or two thousandths of an inch is permissible, but any more impairs the film feeding operation.

By the use of this invention wherein the parts have a floating connection instead of being fixedly connected to form a substantially integral unit, an almost perfect adjustment is obtained. Obviously, therefore, this will permit the production of parts which need not be held to such great accuracy as heretofore, With a consequent economy in time and labor, and a greater output, so long as the tolerance or run out is not more than one or two thousandths of an inch.

Changes may be made in the form and arrangement of the several parts described without departing from the spirit and scope of this invention.

What I claim as new, is:

1. In a means to releasably connect an element to a continuously rotatable shaft, for rotation with the shaft, the combination with a rotary shaft having a key-way; and an element having an axial bore to accommodate the shaft and a radial opening leading from the periphery of said element to its bore; of a pre-set key having a driving fit in the radial opening, the inner end of the key protruding part-way into the key way and being reduced to provide a chamber between the reduced inner end of the key and the wall of the radial opening to accommodate burrs, said reduced inner end having a sliding engagement with the key-way; a stop member to limit movement of the element longitudinally of the shaft in one direction; and a resilient means contacted by the element in its movement along the shaft in the opposite direction.

2. The combination, with a rotatable shaft having a key-way extending longitudinally of the shaft from the outer end thereof, of an element having an axial bore accommodating said shaft slidingly, said element also having a radially extending unthreaded passage from its periphery to its axial bore; an unthreaded, normally non-removable key-pin of slightly larger diameter than said passage, said key-pin being forcibly driven, the inner end of said key-pin being of substantially the same Width as said keyway and extending only part-way into the axial bor of said element to clear the bottom of the key-way and to slide along the key-way to enable the ready application and removal of said element relative to said shaft; and means for releasably retaining said element on said shaft.

3. The combination, with a shaft bearing; and a shaft rotatably supported in the shaft bearing, and having a longitudinal key-way extending inwardly from one end of the shaft; of an element having an axial bore and fitting slidably over said shaft about said key-way, said element being provided with a radial bore extending from the periphery to said axial bore thereof; an unthreaded key-pin of slightly larger diameter than said bore forcibly driven into said radial bore, the inner end of said key-pin being of a width to fit slidingly in said key-way, and protruding partway only into said key-way to clear the bottom thereof; said shaft having a circumferential groove between the inner, end of said element and said bearing; a split ring of greater overall diameter than said shaft fitted snugly into said groove to afford a fixed abutment to space the inner end of said element apart from the exposed end of said shaft bearing; a cupped resilient washer interposed between the inner end of said rotatable element and said split ring; and retaining means engaged with the outer end of said shaft and said rotatable element to press the latter against said cupped resilient washer.

HENRY F. HEIDE'GGER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name I Date 465,175 Geisinger Dec. 15, 1891 1,192,404 Ewart July 25, 1916 1,445,830 Gifford Feb. 20, 1923 2,331,647 Barkstrom et a1. Oct. 12, 1943 FOREIGN PATENTS Number Country Date 360,770 Great Britain MW- Nov, 12. 1931 

